EGF receptor expression, regulation, and function in breast cancer

A Novel Attention-Mechanism Based Cox Survival Model by Exploiting Pan-Cancer Empirical Genomic Information

Cancer prognosis is an essential goal for early diagnosis, biomarker selection, and medical therapy. In the past decade, deep learning has successfully solved a variety of biomedical problems. However, due to the high dimensional limitation of human cancer transcriptome data and the small number of training samples, there is still no mature deep learning-based survival analysis model that can completely solve problems in the training process like overfitting and accurate prognosis. Given these problems, we introduced a novel framework called SAVAE-Cox for survival analysis of high-dimensional transcriptome data. This model adopts a novel attention mechanism and takes full advantage of the adversarial transfer learning strategy. We trained the model on 16 types of TCGA cancer RNA-seq data sets. Experiments show that our module outperformed state-of-the-art survival analysis models such as the Cox proportional hazard model (Cox-ph), Cox-lasso, Cox-ridge, Cox-nnet, and VAECox on the concordance index. In addition, we carry out some feature analysis experiments. Based on the experimental results, we concluded that our model is helpful for revealing cancer-related genes and biological functions.

EGF-Induced miR-223 Modulates Goat Mammary Epithelial Cell Apoptosis and Inflammation via ISG15

The health of mammary gland is essential for lactation. Epidermal growth factor (EGF) is reported to play an important role in lactation initiation and miR-223 is a conserved microRNA in anti-inflammation. In this study, EGF was found to induce a higher expression of miR-223 in goat mammary epithelial cell (gMEC). The downstream genes of miR-223 were screened by RNA sequencing, including Interferon-stimulated gene product 15 (ISG15), a pivotal immune responder, which was detected to be downregulated by EGF and miR-223. Due to the correlation between inflammation and apoptosis, the gMEC apoptosis modulated by EGF, miR-223, and ISG15 was investigated, and the protein expressions of Bcl-2/Bax, Caspase 3 and p53 were examined to evaluate the apoptosis of gMEC. The protein expressions of p-STAT3/STAT3, PR, FOXC1, and HOXA10, which had been shown to be related to inflammation, were detected to assess the inflammation of gMEC. This study provided a regulation axis, EGF/miR-223/ISG15, and illustrated its regulation to gMEC apoptosis and inflammation.

Geranylgeranyl transferase 1 inhibitor GGTI‑298 enhances the anticancer effect of gefitinib

Dysregulation of epidermal growth factor receptor (EGFR) signaling is responsible for the resistance to EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib, and is thereby associated with the progression of tumors in non‑small cell lung cancers (NSCLCs). Immunoblotting results revealed that geranylgeranyl transferase 1 inhibitor (GGTI)‑298, a geranylgeranyl transferase 1 inhibitor with potential antitumor effects, effectively inhibited the phosphorylation of EGFR and its downstream target protein kinase B (AKT). A combination of gefitinib and GGTI‑298 amplified the inhibition of the EGFR‑AKT signaling pathway. In addition, GGTI‑298 treatment produced a synergistic effect on the inhibition of proliferation as indicated by the combination index values of <1 when combined with gefitinib in the NSCLC cell lines HCC827 and A549. These synergistic effects were also observed to induce apoptosis and migration inhibition. Further mechanistic studies demonstrated that GGTI‑298 inhibited the activity of Ras homolog family member A (RhoA), and downregulation of RhoA with small interfering RNA impaired the phosphorylation of EGFR, which suggested that EGFR inhibition by GGTI‑298 may be exerted mainly through RhoA mediation. These results presented a novel, promising therapeutic strategy involving a combination of two drugs for targeting EGFR signaling in lung cancer.

The MYC oncogene is a global regulator of the immune response

The MYC proto-oncogene is a gene product that coordinates the transcriptional regulation of a multitude of genes that are essential to cellular programs required for normal as well as neoplastic cellular growth and proliferation, including cell cycle, self-renewal, survival, cell growth, metabolism, protein and ribosomal biogenesis, and differentiation. Here, we propose that MYC regulates these programs in a manner that is coordinated with a global influence on the host immune response. MYC had been presumed to contribute to tumorigenesis through tumor cell-intrinsic influences. More recently, MYC expression in tumor cells has been shown to regulate the tumor microenvironment through effects on both innate and adaptive immune effector cells and immune regulatory cytokines. Then, MYC was shown to regulate the expression of the immune checkpoint gene products CD47 and programmed death-ligand 1. Similarly, other oncogenes, which are known to modulate MYC, have been shown to regulate immune checkpoints. Hence, MYC may generally prevent highly proliferative cells from eliciting an immune response. MYC-driven neoplastic cells have coopted this mechanism to bypass immune detection. Thus, MYC inactivation can restore the immune response against a tumor. MYC-induced tumors may be particularly sensitive to immuno-oncology therapeutic interventions.

XIAP BIR domain suppresses miR-200a expression and subsequently promotes EGFR protein translation and anchorage-independent growth of bladder cancer cell

BACKGROUND

The X-linked inhibitor of apoptosis protein (XIAP) is a well-known potent apoptosis suppressor and also participates in cancer cell biological behaviors, therefore attracting great attentions as a potential antineoplastic therapeutic target for past years. Anti-IAP therapy is reported to be closely related to epidermal growth factor receptor (EGFR) expression level. However, whether and how XIAP modulates EGFR expression remains largely unknown.

METHODS

Human XIAP was knockdown with short-hairpin RNA in two different bladder cancer cell lines, T24T and UMUC3. Two XIAP mutants, XIAP ∆BIR (deletion of N-terminal three BIR domains) and XIAP ∆RING (deletion of C-terminal RING domain and keeping the function of BIR domains), were generated to determine which domain is involved in regulating EGFR.

RESULTS

We found here that lacking of XIAP expression resulted in a remarkable suppression of EGFR expression, consequently leading to the deficiency of anchorage-independent cell growth. Further study demonstrated that BIR domain of XIAP was crucial for regulating the EGFR translation by suppressing the transcription and expression of miR-200a. Mechanistic studies indicated that BIR domain activated the protein phosphatase 2 (PP2A) activity by decreasing the phosphorylation of PP2A at Tyr307 in its catalytic subunit, PP2A-C. Such activated PP2A prevented the deviant phosphorylation and activation of MAPK kinases/MAPKs, their downstream effector c-Jun, and in turn inhibiting transcription of c-Jun-regulated the miR-200a.

CONCLUSIONS

Our study uncovered a novel function of BIR domain of XIAP in regulating the EGFR translation, providing significant insight into the understanding of the XIAP overexpression in the cancer development and progression, further offering a new theoretical support for using XIAP BIR domain and EGFR as targets for cancer therapy.

Quantification of epidermal growth factor receptor (EGFR) in canine mammary tumours by ELISA assay: clinical and prognostic implications

The involvement of epidermal growth factor receptor (EGFR) is well established in human breast cancer, however, in canine mammary tumours (CMT), including inflammatory mammary carcinomas (IMC), still needs to be clarified. Enzyme immune assay techniques were used for EGFR determinations in tumour tissue from 45 bitches with CMT and in normal mammary glands from eight control dogs. Higher tissue EGFR levels were found in CMT compared with controls (P < 0.05). In malignant CMT, tissue EGFR elevated concentrations were statistically significantly associated with tumour relapse and/or distant metastasis during follow-up and with reduced disease-free and overall survival times. The IMC cases had the highest tissue EGFR levels compared with other malignant non-IMC tumours (P < 0.001). The results support the hypothesis that EGFR levels influence prognosis in malignant CMT, suggesting that EGFR may represent a therapeutic target in cases of high histological aggressiveness and especially in cases of metastatic phenotype and poor prognosis.

Hepatocyte growth factor-like protein is a positive regulator of early mammary gland ductal morphogenesis

The Ron receptor tyrosine kinase regulates multiple cellular processes and is important during mammary gland development and tumor progression. Hepatocyte growth factor-like protein [HGFL] is the only known ligand for the Ron receptor and recent studies have identified major roles for HGFL during breast cancer metastasis. Understanding the functional importance HGFL during mammary gland development will provide significant insights onto its contribution during tumor development and metastasis. In this study, we assessed the role of HGFL during postnatal mammary gland development using mice that were either proficient [HGFL +/+] or deficient [HGFL-/-] for HGFL. Postnatal ductal morphology and stromal cell associations were analyzed at multiple time points through puberty until adulthood. HGFL deficiency resulted in several mammary gland developmental defects including smaller terminal end buds [TEBs], significantly fewer TEBs, and delayed ductal outgrowth during early puberty. Additionally, HGFL deficient animals exhibited significantly altered TEB epithelial cell turnover with decreased proliferation and increased apoptosis coupled with decreased TEB diameter. Macrophage recruitment to the TEBs was also significantly decreased in the HGFL-/- mice compared to controls. Moreover, the levels of STAT3 mRNA as well as the phosphorylation status of this protein were lower in the HGFL-/- mammary glands compared to controls. Taken together, our data provide the first evidence for HGFL as a positive regulator of mammary gland ductal morphogenesis by controlling overall epithelial cell turnover, macrophage recruitment, and STAT3 activation in the developing mammary gland. With a function in early mammary gland development, HGFL represents a potential target for the development of novel breast cancer therapies.

In vivo type 2 cannabinoid receptor-targeted tumor optical imaging using a near infrared fluorescent probe

The type 2 cannabinoid receptor (CB2R) plays a vital role in carcinogenesis and progression and is emerging as a therapeutic target for cancers. However, the exact role of CB2R in cancer progression and therapy remains unclear. This has driven the increasing efforts to study CB2R and cancers using molecular imaging tools. In addition, many types of cancers overexpress CB2R, and the expression levels of CB2R appear to be associated with tumor aggressiveness. Such upregulation of the receptor in cancer cells provides opportunities for CB2R-targeted imaging with high contrast and for therapy with low side effects. In the present study, we report the first in vivo tumor-targeted optical imaging using a novel CB2R-targeted near-infrared probe. In vitro cell fluorescent imaging and a competitive binding assay indicated specific binding of NIR760-mbc94 to CB2R in CB2-mid delayed brain tumor (DBT) cells. NIR760-mbc94 also preferentially labeled CB2-mid DBT tumors in vivo, with a 3.7-fold tumor-to-normal contrast enhancement at 72 h postinjection, whereas the fluorescence signal from the tumors of the mice treated with NIR760 free dye was nearly at the background level at the same time point. SR144528, a CB2R competitor, significantly inhibited tumor uptake of NIR760-mbc94, indicating that NIR760-mbc94 binds to CB2R specifically. In summary, NIR760-mbc94 specifically binds to CB2R in vitro and in vivo and appears to be a promising molecular tool that may have great potential for use in diagnostic imaging of CB2R-positive cancers and therapeutic monitoring as well as in elucidating the role of CB2R in cancer progression and therapy.

Exosomal Proteome Profiling: A Potential Multi-Marker Cellular Phenotyping Tool to Characterize Hypoxia-Induced Radiation Resistance in Breast Cancer

Radiation and drug resistance are significant challenges in the treatment of locally advanced, recurrent and metastatic breast cancer that contribute to mortality. Clinically, radiotherapy requires oxygen to generate cytotoxic free radicals that cause DNA damage and allow that damage to become fixed in the genome rather than repaired. However, approximately 40% of all breast cancers have hypoxic tumor microenvironments that render cancer cells significantly more resistant to irradiation. Hypoxic stimuli trigger changes in the cell death/survival pathway that lead to increased cellular radiation resistance. As a result, the development of noninvasive strategies to assess tumor hypoxia in breast cancer has recently received considerable attention. Exosomes are secreted nanovesicles that have roles in paracrine signaling during breast tumor progression, including tumor-stromal interactions, activation of proliferative pathways and immunosuppression. The recent development of protocols to isolate and purify exosomes, as well as advances in mass spectrometry-based proteomics have facilitated the comprehensive analysis of exosome content and function. Using these tools, studies have demonstrated that the proteome profiles of tumor-derived exosomes are indicative of the oxygenation status of patient tumors. They have also demonstrated that exosome signaling pathways are potentially targetable drivers of hypoxia-dependent intercellular signaling during tumorigenesis. This article provides an overview of how proteomic tools can be effectively used to characterize exosomes and elucidate fundamental signaling pathways and survival mechanisms underlying hypoxia-mediated radiation resistance in breast cancer.

Associations with growth factor genes (FGF1, FGF2, PDGFB, FGFR2, NRG2, EGF, ERBB2) with breast cancer risk and survival: the Breast Cancer Health Disparities Study

Growth factors (GF) stimulate cell proliferation through binding to cell membrane receptors and are thought to be involved in cancer risk and survival. We examined how genetic variation in epidermal growth factor (EGF), neuregulin 2 (NRG2), ERBB2 (HER2/neu), fibroblast growth factors 1 and 2 (FGF1 and FGF2) and its receptor 2 (FGFR2), and platelet-derived growth factor B (PDGFB) independently and collectively influence breast cancer risk and survival. We analyzed data from the Breast Cancer Health Disparities Study which includes Hispanic (2,111 cases, 2,597 controls) and non-Hispanic white (1,481 cases, 1,586 controls) women. Adaptive rank-truncated product (ARTP) analysis was conducted to determine gene significance. Odds ratios (OR) and 95 % confidence intervals were obtained from conditional logistic regression models to estimate breast cancer risk and Cox proportional hazard models were used to estimate hazard ratios (HR) of dying from breast cancer. We assessed Native American (NA) ancestry using 104 ancestry informative markers. We observed few significant associations with breast cancer risk overall or by menopausal status other than for FGFR2 rs2981582. This SNP was significantly associated with ER+/PR+ (OR 1.66, 95 % CI 1.37-2.00) and ER+/PR- (OR 1.54, 95 % CI 1.03-2.31) tumors. Multiple SNPs in FGF1, FGF2, and NRG2 significantly interacted with multiple SNPs in EGFR, ERBB2, FGFR2, and PDGFB, suggesting that breast cancer risk is dependent on the collective effects of genetic variants in other GFs. Both FGF1 and ERBB2 significantly influenced overall survival, especially among women with low levels of NA ancestry (P ARTP = 0.007 and 0.003, respectively). Our findings suggest that genetic variants in growth factors signaling appear to influence breast cancer risk through their combined effects. Genetic variation in ERBB2 and FGF1 appear to be associated with survival after diagnosis with breast cancer.

The role of oncogenes in drug resistance

Increasing evidences indicate that oncogenes can directly or indirectly impact on cancer-cell drug resistance. This chapter provides a conceptual review regarding the role of oncogenes in drug resistance. The review is focused on drug resistance mediated by oncogenes encoding growth factor receptors, signaling molecules, transcription factors, cell-cycle regulators, and apoptosis regulators. It is my hope that better undertsnading on the role of oncogenes in drug resistance will invoke ideas on new approaches to enhance the cytotoxicity of the standard chemotherapeutic agents by functional perturbation of resistance-inducing oncogenes.

Resveratrol modulates MED28 (Magicin/EG-1) expression and inhibits epidermal growth factor (EGF)-induced migration in MDA-MB-231 human breast cancer cells

Resveratrol and pterostilbene exhibit diverse biological activities. MED28, a subunit of the mammalian Mediator complex for transcription, was also identified as magicin, an actin cytoskeleton Grb2-associated protein, and as endothelial-derived gene (EG-1). Several tumors exhibit aberrant MED28 expression, whereas the underlying mechanism is unclear. Triple-negative breast cancers, often expressing epidermal growth factor (EGF) receptor (EGFR), are associated with metastasis and poor survival. The objective of this study is to compare the effect of resveratrol and pterostilbene and to investigate the role of MED28 in EGFR-overexpressing MDA-MB-231 breast cancer cells. Pretreatment of resveratrol, but not pterostlbene, suppressed EGF-mediated migration and expression of MED28 and matrix metalloproteinase (MMP)-9 in MDA-MB-231 cells. Moreover, overexpression of MED28 increased migration, and the addition of EGF further enhanced migration. Our data indicate that resveratrol modulates the effect of MED28 on cellular migration, presumably through the EGFR/phosphatidylinositol 3-kinase (PI3K) signaling pathway, in breast cancer cells.

Epidermal growth factor regulates Mcl-1 expression through the MAPK-Elk-1 signalling pathway contributing to cell survival in breast cancer

Myeloid cell leukaemia-1 (Mcl-1) is an anti-apoptotic member of the Bcl-2 family that is elevated in a variety of tumour types including breast cancer. In breast tumours, increased Mcl-1 expression correlates with high tumour grade and poor patient survival. We have previously demonstrated that Her-2 levels correspond to increased Mcl-1 expression in breast tumours. Epidermal growth factor (EGF) receptor signalling is frequently deregulated in breast cancer and leads to increased proliferation and survival. Herein, we determined the critical downstream signals responsible for the EGF mediated increase of Mcl-1 and their role in cell survival. We found that both Mcl-1 mRNA and protein levels are rapidly induced upon stimulation with EGF. Promoter analysis revealed that an Elk-1 transcription factor-binding site is critical for EGF activation of the Mcl-1 promoter. Furthermore, we found that knockdown of Elk-1or inhibition of the Erk signalling pathway was sufficient to block EGF upregulation of Mcl-1 and EGF mediated cell survival. Using chromatin immunoprecipitation and biotin labelled probes of the Mcl-1 promoter, we found that Elk-1 and serum response factor are bound to the promoter after EGF stimulation. To determine whether Mcl-1 confers a survival advantage, we found that knockdown of Mcl-1 expression increased apoptosis whereas overexpression of Mcl-1 inhibited drug induced cell death. In human breast tumours, we found a correlation between phosphorylated Elk-1 and Mcl-1 protein levels. These results indicate that the EGF induced activation of Elk-1 is an important mediator of Mcl-1 expression and cell survival and therefore a potential therapeutic target in breast cancer.

Negative regulation of EGFR-Vav2 signaling axis by Cbl ubiquitin ligase controls EGF receptor-mediated epithelial cell adherens junction dynamics and cell migration

The E3 ubiquitin ligase Casitas B lymphoma protein (Cbl) controls the ubiquitin-dependent degradation of EGF receptor (EGFR), but its role in regulating downstream signaling elements with which it associates and its impact on biological outcomes of EGFR signaling are less clear. Here, we demonstrate that stimulation of EGFR on human mammary epithelial cells disrupts adherens junctions (AJs) through Vav2 and Rac1/Cdc42 activation. In EGF-stimulated cells, Cbl regulates the levels of phosphorylated Vav2 thereby attenuating Rac1/Cdc42 activity. Knockdown of Cbl and Cbl-b enhanced the EGF-induced disruption of AJs and cell motility. Overexpression of constitutively active Vav2 activated Rac1/Cdc42 and reorganized junctional actin cytoskeleton; these effects were suppressed by WT Cbl and enhanced by a ubiquitin ligase-deficient Cbl mutant. Cbl forms a complex with phospho-EGFR and phospho-Vav2 and facilitates phospho-Vav2 ubiquitinylation. Cbl can also interact with Vav2 directly in a Cbl Tyr-700-dependent manner. A ubiquitin ligase-deficient Cbl mutant enhanced the morphological transformation of mammary epithelial cells induced by constitutively active Vav2; this effect requires an intact Cbl Tyr-700. These results indicate that Cbl ubiquitin ligase plays a critical role in the maintenance of AJs and suppression of cell migration through down-regulation of EGFR-Vav2 signaling.

Minireview: role of kinases and chromatin remodeling in progesterone signaling to chromatin

Steroid hormones regulate gene expression by interaction of their receptors with hormone-responsive elements on DNA or with other transcription factors, but they can also activate cytoplasmic signaling cascades. Rapid activation of Erk by progestins via an interaction of the progesterone receptor (PR) with the estrogen receptor is critical for transcriptional activation of the mouse mammary tumor virus (MMTV) promoter and other progesterone target genes. Erk activation leads to the phosphorylation of PR, activation of mitogen- and stress-activated protein kinase 1, and the recruitment of a complex of the three activated proteins and of P300/CBP-associated factor (PCAF) to a single nucleosome, resulting in the phosphoacetylation of histone H3 and the displacement of heterochromatin protein 1γ. Hormone-dependent gene expression requires ATP-dependent chromatin remodeling complexes. Two switch/sucrose nonfermentable-like complexes, Brahma-related gene 1-associated factor (BAF) and polybromo-BAF are present in breast cancer cells, but only BAF is recruited to the MMTV promoter and cooperates with PCAF during activation of hormone-responsive promoters. PCAF acetylates histone H3 at K14, an epigenetic mark recognized by BAF subunits, thus anchoring the complex to chromatin. BAF catalyzes localized displacement of histones H2A and H2B, facilitating access of nuclear factor 1 and additional PR complexes to the hidden hormone-responsive elements on the MMTV promoter. The linker histone H1 is a structural component of chromatin generally regarded as a general repressor of transcription. However, it contributes to a better regulation of the MMTV promoter by favoring a more homogeneous nucleosome positioning, thus reducing basal transcription and actually enhancing hormone induced transcription. During transcriptional activation, H1 is phosphorylated and displaced from the promoter. The kinase cyclin-dependent kinase 2 is activated after progesterone treatment and could catalyze progesterone-induced phosphorylation of histone H1 by chromatin remodeling complexes. The initial steps of gene induction by progestins involve changes in the chromatin organization of target promoters that require the activation of several kinase signaling pathways initiated by membrane anchored PR. Because these pathways also respond to other external signals, they serve to integrate the hormonal response in the global context of the cellular environment.

EGFR may couple moderate alcohol consumption to increased breast cancer risk

Alcohol consumption is an established risk factor for breast cancer. Nonetheless, the mechanism by which alcohol contributes to breast tumor initiation or progression has yet to be definitively established. Studies using cultured human tumor cell lines have identified signaling molecules that may contribute to the effects of alcohol, including reactive oxygen species and other ethanol metabolites, matrix metalloproteases, the ErbB2/Her2/Neu receptor tyrosine kinase, cytoplasmic protein kinases, adenylate cyclase, E-cadherins, estrogen receptor, and a variety of transcription factors. Emerging data suggest that the epidermal growth factor receptor (EGFR) tyrosine kinase may contribute to breast cancer genesis and progression. Here we integrate these findings and propose three mechanisms by which alcohol contributes to breast cancer. A common feature of these mechanisms is increased EGFR signaling. Finally, we discuss how these mechanisms suggest strategies for addressing the risks associated with alcohol consumption.

Antisense Ki-67 cDNA transfection reverses the tumorigenicity and induces apoptosis in human breast cancer cells

Effects of antisense Ki-67 cDNA transfection on breast cancer cells were investigated in this study. Transfection of antisense Ki-67 cDNA resulted in a 70%-80% reduction in proliferation of MDA-MB-435s, cells which highly expressed Ki-67 mRNA and protein. Transwell assay showed that mobility and invasion capability was dramatically inhibited by 50%-60%, and cell cycle analysis displayed a higher proportion in G(2)/M and G(0)/G(1) phases accompanied by remarkably increased ratio of apoptotic cells. Our results suggested that antisense Ki-67 cDNA vector treatment might be an important potential option in the anticancer therapy.

MMTV-EGF receptor transgene promotes preneoplastic conversion of multiple steroid hormone-responsive tissues

Correlative analyses of tumors and patient-derived cell lines of the human reproductive system suggest that overexpression of EGF contributes to the oncogenic phenotype. However, it is unclear at what stage in disease overexpression of the EGFR is most critical. To assess its role as an initiator of reproductive tissue tumor development, transgenic mice were derived with mouse mammary tumor virus (MMTV)-regulated overexpression of the human EGFR. Although elevated expression of the EGFR in hormonally responsive tissues was observed, only one EGFR transgenic mouse developed a visible tumor over a 2-year period. However, of 12 females monitored over the same time, hyperplasia, hypertrophy, or slight dysplasia was found in mammary glands of 55% of the animals examined, in the uterus or uterine horn of 89%, and in ovaries or oviducts of 100%. None of the reproductive tissues of the male transgenic animals or age-matched, normal mice displayed these changes. These results revealed a role for the EGFR in the initiation of ovarian and uterine cancer and supported previous studies in breast cancer that the receptor can contribute to the neoplastic process in a significant albeit incremental way.

Shedding of epidermal growth factor receptor is a regulated process that occurs with overexpression in malignant cells

Soluble isoforms of the epidermal growth factor receptor (sEGFR) previously have been identified in the conditioned culture media (CCM) of the vulvar adenocarcinoma cell line, A431 and within exosomes of the keratinocyte cell line HaCaT. Here, we report that the extracellular domain (ECD) of EGFR is shed from the cell surface of human carcinoma cell lines that express 7x10(5) receptors/cell or more. We purified this proteolytic isoform of EGFR (PI-sEGFR) from the CCM of MDA-MB-468 breast cancer cells. The amino acid sequence of PI-sEGFR was determined by reverse-phase HPLC nano-electrospray tandem mass spectrometry of peptides generated by trypsin, chymotrypsin or GluC digestion. The PI-sEGFR protein is identical in amino acid sequence to the EGFR ECD. The release of PI-sEGFR from MDA-MB-468 cells is enhanced by phorbol 12-myristate 13-acetate, heat-inactivated fetal bovine serum, pervanadate, and EGFR ligands (i.e., EGF and TGF-alpha). In addition, 4-aminophenylmercuric acetate, an activator of metalloproteases, increased PI-sEGFR levels in the CCM of MDA-MB-468 cells. Inhibitors of metalloproteases decreased the constitutive shedding of EGFR while the PMA-induced shedding was inhibited by metalloprotease inhibitors, by the two serine protease inhibitors leupeptin and 3,4-dichloroisocoumarin (DCI), and by the aspartyl inhibitor pepstatin. These results suggest that PI-sEGFR arises by proteolytic cleavage of EGFR via a mechanism that is regulated by both PKC- and phosphorylation-dependent pathways. Our results further suggest that when proteolytic shedding of EGFR does occur, it is correlated with a highly malignant phenotype.

Unraveling the microenvironmental influences on the normal mammary gland and breast cancer

The normal mammary gland and invasive breast tumors are both complex 'organs' composed of multiple cell types as well as extracellular matrix in three-dimensional (3D) space. Conventionally, both normal and malignant breast cells are studied in vitro as two-dimensional monolayers of epithelial cells, which results in the loss of structure and tissue function. Many laboratories are now investigating regulation of signaling function in the normal mammary gland using 3D cultures. However, it is also important to assay malignant breast cells ex vivo in a physiologically relevant environment to more closely mimic tumor architecture, signal transduction regulation and tumor behavior in vivo. Here we present the potential of these 3D models for drug testing, target validation and guidance of patient selection for clinical trials. We also argue that in order to get full insight into the biology of the normal and malignant breast, and to create in vivo-like models for therapeutic approaches in humans, we need to continue to create more complex heterotypic models to approach the full context the cells encounter in the human body.

Transgenic models to study actions of prolactin in mammary neoplasia

Transgenic models to explore the role of prolactin and its interactions with other factors in mammary oncogenesis have begun to reveal the dynamic contributions of prolactin to the development and progression of this disease. Targeting prolactin to mammary epithelial cells mimics the local production of this hormone that is prominent in women, and permits studies in the absence of effects on the ovarian steroid milieu. These models have demonstrated that local production of prolactin is sufficient to induce mammary tumors after a long latency. Prolactin also can potentiate actions of other oncogenic stimuli, decreasing tumor latency and increasing incidence in several models. Augmented proliferation, without alteration of apoptosis, is a consistent feature. Pathways in addition to the well-characterized Jak2-Stat5 pathway, including ERK1/2 and Akt1/2, are implicated in these actions. These studies have also revealed a complex relationship with estrogen; while prolactin increases ERalpha expression, it does not require estrogenic ligand for lesion development, and indeed, in combination with the EGFR ligand, TGFalpha, prolactin can contribute to estrogen insensitivity. These studies highlight the utility of these models to decipher the interplay between prolactin and other oncogenic factors in breast cancer, with implications for preventative and therapeutic strategies.

Design, synthesis, antitumor evaluations and molecular modeling studies of novel 3,5-substituted indolin-2-one derivatives

AIM

To design and synthesize a novel class of antitumor agents, featuring the 3, 5-substituted indolin-2-one framework.

METHODS

Based on enzyme binding features of (Z)-SU5402, introducing a beta-pyrrole group at the 3-position of the indolin- 2-one core, a series of novel 3,5-substituted indolin-2-ones were designed and synthesized. Four human carcinoma cell lines of A-431, A-549, MDA-MB-468, and Autosomal Dominant Polycystic Kidney disease were chosen for the cell proliferation assay.

RESULTS

Twenty new compounds (1a-t) with E configuration have been designed, synthesized and bioassayed. Their structural features were determined by nuclear magnetic resonance (NMR) spectra, low- and high-resolution mass spectra, and confirmed by X-ray crystallography. Although the enzyme assay showed a weak inhibition effect against the epidermal growth factor receptor, vascular endothelial growth factor receptor, fibroblast growth factor receptor and platelet-derived growth factor receptor tyrosine kinases, the cell-based antitumor activity was promising. Compounds 1 g and 1 h showed higher inhibitory activity toward the A-549 and MDA-MB-468 cell lines with IC(50 ) of 0.065-9.4 micromol/L.

CONCLUSION

This study provides a new template for further development of potent antitumor drugs.

Cross-talk between epidermal growth factor receptor and hypoxia-inducible factor-1alpha signal pathways increases resistance to apoptosis by up-regulating survivin gene expression

Although increasing evidence supports a link between epidermal growth factor receptor (EGFR) signaling and resistance to apoptosis, the mechanism by which the EGFR signaling pathway inhibits apoptosis is not well understood. In this study, we found that epidermal growth factor (EGF) stimulation increased the level of expression of the inhibitor of apoptosis protein survivin in breast cancer cells but not in normal mammary epithelial cells. We further demonstrated that activation of survivin gene expression is mediated by oxygen-independent hypoxia-inducible factor (HIF)-1alpha up-regulation in EGF-treated cancer cells. EGFR signaling activated the phosphoinositide 3-kinase/AKT pathway, subsequently increasing the level of HIF-1alpha under normoxic conditions. HIF-1alpha then activated survivin gene transcription through direct binding to the survivin promoter. Furthermore, we found that overexpression of HIF-1alpha small interfering RNA blocks EGF-induced survivin gene up-regulation and increases apoptosis induced by the chemotherapy drug docetaxel. However, transfection of a plasmid expressing HIF-1alpha gene activates survivin gene expression and reduces the apoptotic response. Our results demonstrate a novel pathway for EGFR signaling-mediated apoptosis resistance in human cancer cells. Although the role of HIF-1alpha in regulating cell survival under hypoxic conditions has been studied extensively, our results show that normoxic breast cancer cells utilize cross-talk between EGFR signals and HIF-1alpha to up-regulate the anti-apoptotic survivin gene, providing a strong rationale for the targeting of HIF-1alpha as a therapeutic approach for both hypoxic and normoxic tumor cells. Understanding key molecular events in EGFR signaling-induced apoptosis resistance should provide new information for the development of novel therapeutic agents targeting EGFR, HIF-1alpha, and/or survivin.

Tannic Acid, a Potent Inhibitor of Epidermal Growth Factor Receptor Tyrosine Kinase

Increasing evidence supports the hypothesis that tannic acid, a plant polyphenol, exerts anticarcinogenic activity in chemically induced cancers. In the present study, tannic acid was found to strongly inhibit tyrosine kinase activity of epidermal growth factor receptor (EGFr) in vitro (IC50 = 323 nM). In contrast, the inhibition by tannic acid of p60(c-src) tyrosine kinase (IC50 = 14 microM) and insulin receptor tyrosine kinase (IC50 = 5 microM) was much weaker. The inhibition of EGFr tyrosine kinase by tannic acid was competitive with respect to ATP and non-competitive with respect to peptide substrate. In cultured cells, growth factor-induced tyrosine phosphorylation of growth factor receptors, including EGFr, platelet-derived growth factor receptor, and basic fibroblast growth factor receptor, was inhibited by tannic acid. No inhibition of insulin-induced tyrosine phosphorylation of insulin receptor and insulin-receptor substrate-1 was observed. EGF-stimulated growth of HepG2 cells was inhibited in the presence of tannic acid. The inhibition of serine/threonine-specific protein kinases, including cAMP-dependent protein kinase, protein kinase C and mitogen-activated protein kinase, by tannic acid was only detected at relatively high concentration, IC50 being 3, 325 and 142 microM respectively. The molecular modeling study suggested that tannic acid could be docked into the ATP binding pockets of either EGFr or insulin receptor. These results demonstrate that tannic acid is an in vitro potent inhibitor of EGFr tyrosine kinase.

Epidermal growth factor receptor overexpression results in increased tumor cell motility in vivo coordinately with enhanced intravasation and metastasis

Although overexpression of the epidermal growth factor receptor (EGFR; ErbB1) has been correlated with poor prognosis in breast and other cancers, clinical trials of ErbB1 inhibitors have shown limited efficacy in inhibiting tumor proliferation. To evaluate other possible roles of ErbB1 in tumor malignancy besides proliferation, we have developed a series of tools for analysis of intravasation. Overexpression of ErbB1 in MTLn3 mammary adenocarcinoma cells results in increased intravasation and lung metastasis from tumors formed by injection of cells in the mammary fat pad. However, increased ErbB1 expression has no effect on primary tumor growth and lung seeding efficiency of cells injected i.v. Chemotactic responses to low concentrations of EGF in vitro and cell motility in vivo in the primary tumor measured using intravital imaging are significantly increased by ErbB1 overexpression. The increased cell motility is restricted to ErbB1-overexpressing cells in tumors containing mixtures of cells expressing different ErbB1 levels, arguing for a cell-autonomous effect of increased ErbB1 expression rather than alteration of the tumor microenvironment. In summary, we propose that ErbB1 overexpression makes more significant contributions to intravasation than growth in some tumors and present a novel model for studying ErbB1 contributions to tumor metastasis via chemotaxis and intravasation.

Molecular pathogenesis of chronic wounds: the role of beta-catenin and c-myc in the inhibition of epithelialization and wound healing

Lack of understanding of the molecular mechanisms and pathogenesis of impaired healing in chronic ulcers is a serious health issue that contributes to excessive limb amputations and mortality. Here we show that beta-catenin and its downstream targets in keratinocytes, c-myc, and keratins K6 and K16, play important roles in the development of chronic wounds. In contrast to normal epidermis, we observed a significant nuclear presence of beta-catenin and elevated c-myc expression at the nonhealing wound edge of chronic ulcers from 10 patients. In vitro studies indicated that stabilization of nuclear beta-catenin inhibited wound healing and keratinocyte migration by blocking epidermal growth factor response, inducing c-myc and repressing the K6/K16 keratins (cytoskeletal components important for migration). The molecular mechanism of K6/K16 repression involved beta-catenin and arginine methyltransferase (CARM-1) acting as co-repressors of glucocorticoid receptor monomers. We conclude that activation of the beta-catenin/c-myc pathway(s) contributes to impaired healing by inhibiting keratinocyte migration and altering their differentiation. The presence of activated beta-catenin and c-myc in the epidermis of chronic wounds may serve as a molecular marker of impaired healing and may provide future targets for therapeutic intervention.

Cellular localization of activated N-WASP using a conformation-sensitive antibody

The main regulators of Arp2/3 activity appear to be N-WASP and the other members of the Scar/WAVE family of proteins. We show here that after EGF stimulation, N-WASP is recruited to the nucleation zone of the dynamic leading edge compartment of carcinoma cells, with maximal recruitment of N-WASP within 1 min after EGF stimulation. The timing of N-WASP recruitment mirrors the timing of barbed-end formation at the leading edge. To determine the cellular activation of N-WASP after EGF stimulation, we made a conformation-sensitive antibody (CSA) against the CRIB domain of N-WASP that is predicted to recognize N-WASP in its open, active conformation, but not in its closed, inactive conformation. The ability of CSA to detect only active N-WASP was demonstrated by in vitro experiments using immunoprecipitation of active N-WASP from EGF-stimulated cells and Cdc42 activation of N-WASP activity. In cell staining experiments, N-WASP is maximally accessible to CSA 40 sec after EGF stimulation and this activated N-WASP is in the nucleation zone. These results indicate that active N-WASP is present at the leading edge of lamellipods, an unexpected finding given its reported involvement in filopod formation. This work establishes the feasibility of using antibodies directed against specific conformations or epitopes with changing accessibilities as a window on the status and localization of activity.

A paracrine loop between tumor cells and macrophages is required for tumor cell migration in mammary tumors

Invasion of tumor cells into the surrounding connective tissue and blood vessels is a key step in the metastatic spread of breast tumors. Although the presence of macrophages in primary tumors is associated with increased metastatic potential, the mechanistic basis for this observation is unknown. Using a chemotaxis-based in vivo invasion assay and multiphoton-based intravital imaging, we show that the interaction between macrophages and tumor cells facilitates the migration of carcinoma cells in the primary tumor. Gradients of either epidermal growth factor (EGF) or colony-stimulating factor 1 (CSF-1) stimulate collection into microneedles of tumor cells and macrophages even though tumor cells express only EGF receptor and macrophages express only CSF-1 receptor. Intravital imaging shows that macrophages and tumor cells migrate toward microneedles containing either EGF or CSF-1. Inhibition of either CSF-1- or EGF-stimulated signaling reduces the migration of both cell types. This work provides the first direct evidence for a synergistic interaction between macrophages and tumor cells during cell migration in vivo and indicates a mechanism for how macrophages may contribute to metastasis.

Forkhead box transcription factor FOXO3a regulates estrogen receptor alpha expression and is repressed by the Her-2/neu/phosphatidylinositol 3-kinase/Akt signaling pathway

The expression status of the estrogen receptor alpha (ERalpha) and that of the epidermal growth factor receptor Her-2/neu frequently correlate inversely in breast cancers. While ERalpha-dependent cancers respond to antiestrogen therapy, Her-2/neu-overexpressing cancers typically display resistance to antiestrogens and poor prognosis. In this report we have explored the mechanism linking the loss of expression of ERalpha in breast cancer cells with overexpression of Her-2/neu, which signals constitutively via a phosphatidylinositol 3-kinase (PI3K)/Akt kinase pathway. We identify for the first time the Forkhead box protein FOXO3a (formerly termed FKHRL-1), which is inactivated by Akt, as a key regulator of ERalpha gene transcription. In breast cancer cell lines, expression of ERalpha was correlated with active FOXO3a levels. Ectopic FOXO3a expression induced ERalpha protein levels and promoter activity, while a dominant negative FOXO3a decreased ERalpha levels. By using transient transfection, mobility shift assays, and site-directed mutagenesis, two major functional Forkhead binding sites were identified in the human ERalpha promoter B. A chromatin immunoprecipitation assay confirmed FOXO3a binding at these two sites. Ectopic FOXO3a induced estrogen response element-driven reporter activity and expression of ERalpha target genes. The constitutively activated myristylated Akt reduced ERalpha expression, whereas agents that negatively affect the PI3K/Akt pathway, i.e., wortmannin, celecoxib, and the green tea polyphenol epigallocatechin-3 gallate, induced ERalpha. Thus, FOXO3a represents an important intracellular mediator of ERalpha expression, suggesting possible therapeutic intervention strategies for Her-2/neu-overexpressing refractory breast tumors.

Growth and EGFR Regulation in Breast Cancer Cells by Vitamin D and Retinoid Compounds

The effect of 1,25-dihydroxyvitamin D(3), analog C (1,25-(OH)(2)-16-en-23-yn-26,27-F(6)-vitamin D(3)), 9-cis retinoic acid, and all-trans retinoic acid on the growth and expression of EGFR in MCF7, T47D, BT474, and BT549 breast cancer cells was examined. Significant growth inhibition was noted in MCF7, T47D, and BT474 cells by 8 days of treatment, while BT549 cells showed none. MCF7, T47D, and BT549 cells treated with 1,25-dihydroxyvitamin D(3) demonstrated a 50% decrease in EGFR mRNA within 2 h which was sustained to 72 h, while BT474 cells demonstrated a 200-500% increase. EGFR protein levels correlated with these mRNA changes in BT474 and BT549 cells. Measurement of mRNA stability in vitamin D treated BT474 cells indicated that there was no change in EGFR mRNA half-life. Transfection of an EGFR promoter containing reporter plasmid demonstrated vitamin D induced changes in reporter gene activity that paralleled the changes observed in EGFR mRNA and protein. Electrophoretic mobility shift assays using a putative vitamin D response element within this region of the EGFR promoter demonstrated specific VDR binding. These results indicate that the vitamin D effect on EGFR expression in breast cancer cells has a transcriptional component likely mediated through a vitamin D responsive promoter sequence. They also suggest that growth inhibition and EGFR down-regulation by vitamin D and retinoids may be related events in some breast cancer cells, but not in all.

Elucidating inhibitory models of the inhibitors of epidermal growth factor receptor by docking and 3D-QSAR

Epidermal growth factor receptor (EGFR) protein tyrosine kinases (PTKs) are attractive targets for anti-tumor drug design. Although thousands of their ligands have been studied as potential inhibitors against PTKs, there is no QSAR study that covers different kinds of inhibitors with observable structural diversity. However, by using this approach, we could mine far more useful information. Hence in order to better understand the binding model and the relationship between the physicochemical properties and the inhibitory activities of different kind of various inhibitors, molecular docking and 3D-QSAR, viz. CoMFA and CoMSIA, were combined to study 124 reported inhibitors with different scaffolds. Based on the docked binding conformations, highly reliable and predictive 3D-QSAR models were derived, which reveal how steric, electrostatic, and hydrophobic interactions contribute to inhibitors' bioactivities. This result also demonstrates that it is possible to include different kinds of inhibitors with observable structural diversity into one 3D-QSAR study. Therefore, this study not only casts light on binding mechanism between EGFR and its inhibitors, but also provides new hints for de novo design of new EGFR inhibitors with observable structural diversity.

The characteristics of malignant breast tumors in hormone replacement therapy users versus nonusers

BACKGROUND

The purpose of this study was to investigate the characteristics of breast cancer in hormone replacement therapy (HRT) users vs. nonusers.

METHODS

We investigated the characteristics of all patients between the ages of 50 and 75 years with breast tumors. Then, an age-adjusted group of 55 nonusers was chosen to match and compare with HRT users.

RESULTS

Of the 243 patients available for evaluation, 55 (22.6%) used HRT. Disease stages in HRT users vs. nonusers were as follows: ductal carcinoma in situ (DCIS), 20% and 17.1%; stage I, 45.5% and 41.7%; stage II, 30.9% and 26.2%; stage III, 3.6% and 13.4%; and stage IV, 0% and 1.6% (P =.27). In the age-adjusted cohort, stages in nonusers were as follows: DCIS, 7.3%; stage I, 47.3%; stage II, 25.5%; stage III, 20%; and stage IV, 0% (P =.03). Tumor grades in HRT users vs. nonusers were as follows: grade I, 30.4% and 15.7%; grade II, 52.2% and 52.2%; and grade III, 17.4% and 32.1% (P =.035). Grades in cohort nonusers were as follows: I, 13.2%; II, 52.8%; and III, 34% (P =.05). In the invasive tumors, the positive estrogen receptor (ER) rates were 81.6% and 85.7% (P =.89); positive progesterone receptor (PR) rates were 53.1% and 54% (P =.95); and Her 2-neu positive rates were 18.4% and 17.6% (P =.95), respectively. No significant difference was found in intratumor DCIS, vascular invasion, and Ki-67 (P =.14,.9, and.79, respectively). The rate of lobular and favorable histological types was higher in the HRT user group: 26.6% vs. 15%.

CONCLUSIONS

Breast tumors in HRT users vs. nonusers were of a significantly lower stage and grade and accounted for a higher number of favorable histological types, but all other parameters were similar in the two groups.

MAP kinases couple multiple functions of human progesterone receptors: degradation, transcriptional synergy, and nuclear association

Breast cancers often have increased mitogen-activated protein kinase (MAPK) activity; this pathway influences breast cancer cell growth in part by targeting steroid hormone receptors. Bidirectional cross-talk between these two pathways is well documented; progestins increase the expression of type I growth factor receptors that couple to MAPK activation, and in turn, activation of p42 and p44 MAPKs increases ligand-dependent progesterone receptor (PR) transcriptional activity, and parodoxically, augments PR downregulation. Breast cancers that have become steroid hormone resistant often remain highly sensitive to growth factors. We believe that the mechanism of steroid hormone resistance is biochemically linked to the acquisition of growth factor responsiveness. Using in vitro models, we have established numerous regulatory links between signal transduction pathways elicited by peptide growth factors and PR. Of note is the role of phosphorylation of human PRs by MAPKs. Phosphorylation of PR on a key serine residue (Ser294) by MAPKs couples multiple receptor functions, including ligand-dependent PR downregulation by the ubiquitin-proteasome pathway, transcriptional synergy between progestins and growth factors, and nuclear localization of PR proteins. Linkage of these events suggests a mechanism for steroid hormone receptor "hypersensitivity" induced by growth factors. The uncoupling of these events during breast cancer progression is predicted to profoundly influence hormone responsiveness, as PR with altered stability may be driven primarily by upregulated growth factors.

Induction of EGF-dependent apoptosis by vacuolar-type H(+)-ATPase inhibitors in A431 cells overexpressing the EGF receptor

The stimulation of human tumor cells overexpressing epidermal growth factor receptor (EGFR) with EGF enhances tumor development and malignancy. Therefore, compounds that modulate the EGF-mediated signal inducing apoptosis in EGFR-overexpressing cells would represent a new class of antitumor drug and might be useful in the treatment of a subset of human tumors. In the course of screening for compounds that induce apoptosis in EGFR-overexpressing human epidermal carcinoma A431 cells from secondary metabolites of microorganisms, we found that vacuolar-type H(+)-ATPase (V-ATPase) inhibitors, such as concanamycin B and destruxin E, induced apoptosis only when the cells were stimulated with EGF. The EGF-dependent apoptosis by V-ATPase inhibitors was not observed in other types of human tumor cells which do not overexpress EGFR. The apoptosis in A431 cells was inhibited by anti-FasL antibody which neutralized the cytotoxic effect of FasL, indicating that the Fas/FasL system was involved. The expression of cell surface FasL was upregulated by stimulation with EGF and increased further by V-ATPase inhibitors. Moreover, EGF inhibited cytotoxic Fas antibody-induced apoptosis, whereas V-ATPase inhibitors disrupted the protective effect of EGF on apoptosis in A431 cells. Taken together, these results suggested that V-ATPase inhibitors induced EGF-dependent apoptosis in A431 cells, possibly through both the enhancement of EGF-induced cell surface expression of FasL and the disruption of an EGF-induced survival signal.

The use of molecular markers in farnesyltransferase inhibitor (FTI) therapy of breast cancer

The hypothesis that pharmacologic inhibitors of Ras can be effective anti-cancer agents has led to the development of Farnesyltransferase inhibitors (FTIs). These agents inhibit the requisite processing of a number of cellular proteins including Ras. FTIs have shown good anti-tumor efficacy and little toxicity in preclinical models and based on these results, numerous clinical trials are currently underway to evaluate the clinical potential of these agents in patients with cancer. However, contrary to the ideas that led to their design, mechanistic studies have not confirmed that they inhibit tumors through the inhibition of Ras. FTIs inhibit the growth of a broad variety of human tumor cells in vitro and studies to date have not identified cellular characteristics that predict the antitumor efficacy of this class of agents. We have studied a panel of breast cancer cell lines that differ widely in their sensitivity to FTI in order to determine which molecular characteristics may determine sensitivity to this class of agents. In these cells we find that FTI sensitivity does not correlate with the relative expression of Ras isoforms or the inhibition of Ras processing, growth factor signaling, expression of estrogen receptor or the overexpression of growth factor receptors. Looking for other molecular correlates of FTI sensitivity we have compared the activity of farnesylprotein transferase (FPTase) among these cells and although we find no overall correlation with FTI sensitivity, we find that two cell lines with unusually low FPTase activity are sensitive. Comparing p53 genotype with FTI-sensitivity we find that although most cell lines in our panel have mutant p53, all three cell lines with wild-type p53 are quite sensitive to FTI. In fact, MCF-7 cells which have both wild-type p53 and the lowest FPTase activity are the most FTI-sensitive cell type we have ever seen. Although these studies do not identify any single molecular marker that can accurately predict FTI sensitivity in breast tumors, they highlight the potential roles of FPTase activity and p53 function for further analysis.

Inhibition of epidermal growth factor receptor tyrosine kinase by chalcone derivatives

In our previous study, butein, a chalcone derivative, was found to be an inhibitor of tyrosine kinases and the inhibition was ATP-competitive. In this work, chalcone and seven chalcone derivatives were used to analyse the relationship between the structure of these compounds and their inhibition of tyrosine kinase activity. Three of chalcone derivatives, including butein, marein and phloretin, were found to have an ability to inhibit the tyrosine kinase activity of epidermal growth factor receptor (EGFR) in vitro. IC(50) was 8 microM for butein, 19 microM for marein and 25 microM for phloretin. The structural characterisations of these inhibitors suggest that the hydroxylations at C4 and C4' of these molecules may be required for them to act as EGFR tyrosine kinase inhibitors. The inhibition of EGF-induced EGFR tyrosine phosphorylation by butein was also observed in human hepatocellular carcinoma HepG2 cells, while marein and phloretin were inactive at the doses tested. Molecular modelling suggests that butein, marein and phloretin can be docked into the ATP binding pocket of EGFR. Hydrogen bonds and hydrophobic interaction appear to be important in the binding of these inhibitors to EGFR.

VIP receptor antagonists and chemotherapeutic drugs inhibit the growth of breast cancer cells

The effects of vasoactive intestinal peptide (VIP) antagonists on breast cancer cells were investigated. (N-stearyl, norleucine17)VIP hybrid ((SN)VIPhyb) inhibited specific 125I-VIP binding to MCF7, SKBR3, T47D ZR75-1 and MDA-MB231 cells with high affinity (IC50 values of 0.03-0.06 microM). (SN)VIPhyb, 1 microM, inhibited the ability of 10 nM VIP to cause elevation of cAMP and to increase c-fos mRNA. Micromolar concentrations of (SN)VIPhyb inhibited the proliferation of MDA-MB231 or MCF7 cells using a MTT and clonogenic assay. Using a MTT assay, (SN)VIPhyb enhanced the ability of taxol and doxorubicin to inhibit breast cancer growth. Using nude mice bearing MDA-MB231 xenografts, VIPhyb potentiated the ability of taxol to inhibit proliferation. The results indicate that VIP receptor antagonists increase the ability of chemotherapeutic drugs to kill breast cancer cells.

Epidermal growth factor receptor as a genetic therapy target for carcinoma cell radiosensitization

BACKGROUND

Exposure of human cancer cells to ionizing radiation activates the epidermal growth factor receptor (EGFR), which, in turn, mediates a cytoprotective response that reduces the cells' sensitivity to ionizing radiation. Overexpression of a dominant-negative EGFR mutant, EGFR-CD533, disrupts the cytoprotective response by preventing radiation-induced activation of the receptor and its downstream effectors. To investigate whether gene therapy with EGFR-CD533 has the potential to increase tumor cell radiosensitivity, we introduced an adenoviral vector containing EGFR-CD533 into xenograft tumors in nude mice and evaluated the tumor response to ionizing radiation.

METHODS

Xenograft tumors established from the human mammary carcinoma cell line MDA-MB-231 were transduced via infusion with the adenoviral vector Ad-EGFR-CD533 or a control vector containing the beta-galactosidase gene, Ad-LacZ. The transduced tumors were then exposed to radiation in the therapeutic dose range, and radiation-induced EGFR activation was assessed by examining the tyrosine phosphorylation of immunoprecipitated EGFR. Radiosensitization was determined in vitro by colony-formation assays. All statistical tests were two-sided.

RESULTS

The transduction efficiency of MDA-MB-231 tumors by Ad-LacZ was 44%. Expression of EGFR-CD533 in tumors reduced radiation-induced EGFR activation by 2.94-fold (95% confidence interval [CI] = 2.23 to 4.14). The radiosensitivity of Ad-EGFR-CD533-transduced tumors was statistically significantly higher (46%; P<.001) than that of Ad-LacZ-transduced tumors, yielding a dose-enhancement ratio of 1.85 (95% CI = 1.54 to 2.51).

CONCLUSIONS

Transduction of MDA-MB-231 xenograft tumors with Ad-EGFR-CD533 conferred a dominant-negative EGFR phenotype and induced tumor radiosensitization. Therefore, disruption of EGFR function through overexpression of EGFR-CD533 may hold promise as a gene therapeutic approach to enhance the sensitivity of tumor cells to ionizing radiation.

Liposome targeting to tumors using vitamin and growth factor receptors

Liposome-encapsulated anticancer drugs reveal their potential for increased therapeutic efficacy and decreased nonspecific toxicities due to their ability to enhance the delivery of chemotherapeutic agents to solid tumors. Advances in liposome technology have resulted in the development of ligand-targeted liposomes capable of selectively increasing the efficacy of carried agents against receptor-bearing tumor cells. Receptors for vitamins and growth factors have become attractive targets for ligand-directed liposomal therapies due to their high expression levels on various forms of cancer and their ability to internalize after binding to the liposomes conjugated to receptors' natural ligands (vitamins) or synthetic agonists (receptor-specific antibodies and synthetic peptides). This chapter summarizes various strategies and advances in targeting liposomes to vitamin and growth factor receptors in vitro and in vivo with special emphasis on two extensively studied liposome-targeting systems utilizing folate receptor and HER2/neu growth factor receptor.

Selection of cell binding and internalizing epidermal growth factor receptor antibodies from a phage display library

The first step in developing a targeted cancer therapeutic is generating a ligand that binds to a receptor which is either tumor specific or sufficiently overexpressed in tumors to provide targeting specificity. For this work, we generated human monoclonal antibodies to the EGF receptor (EGFR), an antigen overexpressed on many solid tumors. Single chain Fv (scFv) antibody fragments were directly selected by panning a phage display library on tumor cells (A431) overexpressing EGFR or Chinese hamster ovary cells (CHO/EGFR cells) transfected with the EGFR gene and recovering endocytosed phage from within the cell. Three unique scFvs were isolated, two from selections on A431 cells and two from selections on CHO/EGFR cells. All three scFv bound native receptor as expressed on a panel of tumor cells and did not bind EGFR negative cells. Phage antibodies and multivalent immunoliposomes constructed from scFv were endocytosed by EGFR expressing cells as shown by confocal microscopy. Native scFv primarily stained the cell surface, with less staining intracellularly. The results demonstrate how phage antibodies binding native cell surface receptors can be directly selected on overexpressing cell lines or transfected cells. Use of a transfected cell line allows selection of antibodies to native receptors without the need for protein expression and purification, significantly speeding the generation of targeting antibodies to genomic sequences. Depending upon the format used, the antibodies can be used to deliver molecules to the cell surface or intracellularly.

[Expression of the adhesion molecule CD44v6 in infiltrating ductal carcinomas of the breast is associated with hormone dependence. Our experience with 168 cases]

In order to investigate the possible hormone-dependence of CD44v6 in human breast cancer, we assayed the concentrations of this isoform in the membrane fraction of 168 invasive ductal carcinomas (IDC) and in 26 normal breast tissue samples, 18 fibradenomas (FAD), 3 fibrocystic disease specimens (FD), 7 mucinous carcinomas and 4 medullary carcinomas using the ELISA method. The results were compared with those of the estrogen (ER) and progesterone (PR) receptors, pS2, tissue type plasminogen activator (t-PA), cathepsin D, epidermal growth factor receptor (EGFR) and c-erbB2/neu oncoprotein concentrations. Menopausal status, size of the tumor in the cases of cancers, axillary lymph node involvement, histologic grade, ploidy, cellular synthesis phase, multifocality and multicentricity were also considered as variables. The cut-off value for CD44v6-positivity was set at 5 ng/mg prt. membrane protein content. 64/138 (38.1%) infiltrating ductal carcinomas scored positive. This was significantly higher than for the normal breast tissue (0/26; p: 0.0001), similar to that seen in the FAD (3/18), fibrocystic disease (0/3), infiltrating mucinous carcinomas (4/7) and lobular (3/15) and significantly lower than for the infiltrating medullary carcinomas (4/4; p: 0.027). There were no significant differences with the other groups of tissues studied. Furthermore, CD44v6-positive IDC showed significantly higher concentrations of ER, PR and cathepsin D and lower (p: 0.051) concentrations of EGFR when compared to their CD44v6-negative counterparts. The significant coexpression of ER, PR and cathepsin D seems to indicate a possible role for hormonal regulation of CD44v6 expression while the role of pS2 and t-PA, estrogen related proteins, was very reduced.

Prognostic factors in breast cancer. College of American Pathologists Consensus Statement 1999

BACKGROUND

Under the auspices of the College of American Pathologists, a multidisciplinary group of clinicians, pathologists, and statisticians considered prognostic and predictive factors in breast cancer and stratified them into categories reflecting the strength of published evidence.

MATERIALS AND METHODS

Factors were ranked according to previously established College of American Pathologists categorical rankings: category I, factors proven to be of prognostic import and useful in clinical patient management; category II, factors that had been extensively studied biologically and clinically, but whose import remains to be validated in statistically robust studies; and category III, all other factors not sufficiently studied to demonstrate their prognostic value. Factors in categories I and II were considered with respect to variations in methods of analysis, interpretation of findings, reporting of data, and statistical evaluation. For each factor, detailed recommendations for improvement were made. Recommendations were based on the following aims: (1) increasing uniformity and completeness of pathologic evaluation of tumor specimens, (2) enhancing the quality of data collected about existing prognostic factors, and (3) improving patient care.

RESULTS AND CONCLUSIONS

Factors ranked in category I included TNM staging information, histologic grade, histologic type, mitotic figure counts, and hormone receptor status. Category II factors included c-erbB-2 (Her2-neu), proliferation markers, lymphatic and vascular channel invasion, and p53. Factors in category III included DNA ploidy analysis, microvessel density, epidermal growth factor receptor, transforming growth factor-alpha, bcl-2, pS2, and cathepsin D. This report constitutes a detailed outline of the findings and recommendations of the consensus conference group, organized according to structural guidelines as defined.

Inhibition of PC cell-derived growth factor (PCDGF, epithelin/granulin precursor) expression by antisense PCDGF cDNA transfection inhibits tumorigenicity of the human breast carcinoma cell line MDA-MB-468

PC-cell derived growth factor (PCDGF) is an 88-kDa growth factor originally purified from the highly tumorigenic teratoma PC cell line and corresponds to the epithelin/granulin precursor. In teratoma cells, PCDGF expression was shown to be essential for tumorigenicity. We have reported that PCDGF was expressed in estrogen receptor-positive (ER(+)) human mammary epithelial cells in an estrogen-dependent fashion. In this study, we have investigated PCDGF expression in human mammary epithelial cell lines ranging from immortalized nontumorigenic cells to ER(+) and ER(-) breast carcinoma cells. Northern and Western blot analyses indicated that PCDGF mRNA and protein expression was low in nontumorigenic cells and increased in human breast carcinomas cell lines in a positive correlation with their tumorigenicity. Treatment of the ER(-) MDA-MB-468 cells with anti-PCDGF neutralizing antibody resulted in a dose-dependent inhibition of their proliferation, suggesting that secreted PCDGF acted as an autocrine growth factor for breast carcinoma cells. We then examined the in vitro and in vivo growth properties of MDA-MB-468 cells, where PCDGF expression had been inhibited by antisense PCDGF cDNA transfection. Inhibition of PCDGF expression resulted in a reduced proliferation rate in vitro and a 60-80% reduction in colony formation. Tumor formation in vivo was dramatically inhibited in antisense cells with a 90% inhibition of tumor incidence and tumor weight. These results demonstrate the importance of PCDGF overexpression for the proliferation and tumorigenicity of ER(-) breast carcinomas and suggest that PCDGF overexpression may play an important role in human breast cancer.

Human mammary epithelial cells rapidly exchange empty EGFR between surface and intracellular pools

Binding of ligand to the epidermal growth factor receptor (EGFR) initiates a series of processes including activation of the intrinsic EGFR tyrosine kinase, receptor autophosphorylation, and the assembly of active signaling complexes at the plasma membrane. Concomitantly, receptor trafficking is initiated, and the receptor is ultimately delivered to the lysosome, where it is degraded. Virtually all studies on EGFR trafficking have used fibroblasts and transformed cells. Because EGFR exerts a potent effect on the physiology of epithelial cells, we examined the regulation of EGFR activity and trafficking in nontransformed human mammary epithelial cells (HMEC). We found that HMEC that displayed a luminal phenotype were largely unresponsive to EGF and maintained a majority of their EGFR at the cell surface. In contrast, HMEC with a basal phenotype were highly responsive to EGF and, at steady state in the absence of exogenous ligand, distributed empty EGFR into intracellular pools. Maintenance of the intracellular pools was a direct consequence of specific and rapid endocytosis of the empty EGFR. The trafficking pattern was EGFR specific, used coated pits, and did not require receptor tyrosine kinase activity. Such an mechanism redistributes EGFR signaling potential among different membrane domains and into vesicles with unique biochemical microenviroments. In addition, our data show that EGFR endocytosis can be regulated in the absence of ligand binding and receptor activation in a cell-type-specific manner.

Daphnetin, one of coumarin derivatives, is a protein kinase inhibitor

Protein kinases play key roles in the control of cell proliferation, differentiation and metabolism. In this work, we studied the effect of coumarin and its derivatives, including daphnetin, esculin, 2-OH-coumarin, 4-OH-coumarin and 7-OH-coumarin, on the activity of protein kinases. It was found that, in these compounds, only daphnetin was a protein kinase inhibitor. This compound inhibited tyrosine-specific protein kinase, EGF receptor (IC(50) = 7.67 microM), and serine/threonine-specific protein kinases, including cAMP-dependent protein kinase (PKA) (IC(50) = 9.33 microM) and protein kinase C (PKC) (IC(50) = 25.01 microM) in vitro. The inhibition of EGF receptor tyrosine kinase by daphnetin was competitive to ATP and non-competitive to the peptide substrate. The inhibition of EGF-induced tyrosine phosphorylation of EGF receptor by daphnetin was not observed in human hepatocellular carcinoma HepG2 cells. The structural comparison of daphnetin with coumarin and other coumarin derivatives suggests that the hydroxylation at C8 may be required for daphnetin acting as a protein kinase inhibitor.

Epidermal growth factor protects epithelial cells against Fas-induced apoptosis. Requirement for Akt activation

Chemotherapeutic drugs that damage DNA kill tumor cells, in part, by inducing the expression of a death receptor such as Fas or its ligand, FasL. Here, we demonstrate that epidermal growth factor (EGF) stimulation of T47D breast adenocarcinoma and embryonic kidney epithelial (HEK293) cells protects these cells from Fas-induced apoptosis. EGF stimulation of epithelial cells also inhibited Fas-induced caspase activation and the proteolysis of signaling proteins downstream of the EGF receptor, Cbl and Akt/protein kinase B (Akt). EGF stimulation of Akt kinase activity blocked Fas-induced apoptosis. Expression of activated Akt in MCF-7 breast adenocarcinoma cells was sufficient to block Fas-mediated apoptosis. Inhibition of EGF-stimulated extracellular signal-regulated kinase (ERK) activity did not affect EGF protection from Fas-mediated apoptosis. The findings indicate that EGF receptor stimulation of epithelial cells has a significant survival function against death receptor-induced apoptosis mediated by Akt.